Many industrial applications require the grinding and pulverizing of plastic and other polymeric components. A common grinding machine utilizes a circular shaped drive ring, commonly about two feet in diameter, orientated substantially in the plane which is perpendicular to the ground, and which is attached to a motor-driven rotatable shaft. The drive ring has attached to it numerous blade segments, usually a total of between 14 and 60, and each blade segment contains a plurality of blades. In the grinding machines in current use, the segments are attached to the drive ring using at least one direct fastener, such as a bolt. Usually the blade segments are attached using two bolts.
Bolting the blade segments to the drive ring provides a secure connection during the grinding or pulverizing process, but this connection mechanism causes production inefficiency and other problems. When blades are worn, the operator must replace the blade segments. It takes extensive time to replace the blade segments, because each segment must be unbolted and, after sharpening or replacement, re-bolted to the drive ring. Even with automated equipment for removing and installing the bolts, the exchange process can require 4 to 6 hours to complete. Extensive replacement time results in the manufacturer losing machine operation time, or having to invest in a redundant drive ring-blade segment set. This poses a problem to the industrial plastic grinder or pulverizer, because many cannot afford to purchase duplicate drive ring sets for immediate replacement or afford to pay for machine operators to replace blade segments.
Additionally, worn blade segments are sharpened by re-cutting groves into the surface of the blade segment. The bolting mechanism requires that the blade segments contain threaded longitudinal grooves. Threaded grooves require a minimum thickness in the blade segments and, therefore, reduce the width of the blade segment available for resharpening.
A solution to this problem was attempted by eliminating the bolt attachment, and fixing blade segments in place using pressure or clamping, such as disclosed in U.S. Pat. No. 3,941,319. This approach does not provide a complete solution because it relies on clamping or overt pressure to fix the blade segments in place. This approach resulted in additional components that impede the grinding or pulverizing process and, in some cases, failed to adequately fix the blade segments in place.